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प्रश्न
The picture given here shows a person wearing 'half-moon' spectacles. What sort of eye-defect do do you think he has? Why are these particular spectacles useful to him?
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उत्तर
As the person is wearing half-moon spectacles, he should be suffering from the eye defect called long-sightedness, or hypermetropia, because his spectacles are fitted with convex lens. The convex lenses form the images of nearby objects at the near point of his eye, and he can, therefore, see these objects clearly.
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संबंधित प्रश्न
Write the importance of ciliary muscles in the human eye. Name the defect of vision that arises due to gradual weakening of the ciliary muscles. What types of lenses are required by the person suffering from this defect to see the objects clearly?
Akshay, sitting in the last row in his class, could not see clearly the words write on the blackboard. When the teacher noticed it, he announced if any student sitting in the front row could volunteer to exchange his seat with Akshay. Salman immediately agreed to exchange his seat with Akshay. He could now see the words written on the blackboard clearly. The teacher thought it fit to send the message to Akshay’s parents advising them to get his eyesight checked.
In the context of the above event, answer the following questions:-
(a) Which defect of vision is Akshay suffering from? Which type of lens is used to correct this defect?
(b) State the values displayed by the teacher and Salman.
(c) In your opinion, in what way can Akshay express his gratitude towards the teacher and Salman?
List three common refractive defects of vision. Suggest the way of correcting these defects.
What is the far point and near point of the human eye with normal vision?
What is the other name of old age hypermetropia?
Where is the near point of a person suffering from hypermetropia (or long-sightedness)?
A student sitting in the last row of the class-room is not able to read clearly the writing on the blackboard.
Name the type of defect he is suffering from.
Explain with the help of labelled ray diagram, the defect of vision called myopia and how it is corrected by a lens.
A person cannot see the distant objects clearly (though he can see the nearby objects clearly). He is suffering from the defect of vision called:
(a) cataract
(b) hypermetropia
(c) myopia
(d) presbyopia
A person can read a book clearly only if he holds it at an arm's length from him. Name the defect of vision:
if the person is a young man
What is meant by optical illusion? Give one example.
Given below is a diagram depicting a defect of the human eye? Study the same and answer the question that follow:
Give two possible reasons for this defect of the eye in human beings.
Solve the following question:
The near point of the eye of a person is 50 cm. Find the nature and power of the corrective lens required by the person to enable him to see clearly the objects placed at 25 cm from the eye?
Give Reason:
Deficiency of vitamin A causes night blindness.
Give Reason:
When you enter into a dark room from bright because of sunlight, you can not see things for a few seconds.
Explain the Term: Presbyopia
In Myopia the human eye _______.
Draw ray diagram showing myopic eye.
Observe the figure whether it is correct or not and explain the phenomenon.
Name the following:
Two kinds of accomodations.
Have a look at the posture of this girl who is reading a book and answer the questions which follow:
 |
- Name the problem she is facing.
- What are the two conditions shown in sections A and B of the eye as applicable to her.
- What kind of reading glasses does she need?
 |
 |
| A | B |
